1. Field of the Invention
The present invention relates generally to a lighting device and, more specifically, to a light source, such as a grouping of light-emitting-diodes (LEDs), in combination with heat dissipation means and a reflector assembly that reflects the light source emissions into concentrated light paths.
2. Description of the Related Art
Reliable safety lights are critical for the safety of boats to prevent accidental collisions during darkness and inclement weather. A number of attempts have been made to replace marine filament bulbs with LEDs in marine safety lights because of their relatively small power consumption and long life. Incandescent bulbs have a resistively heated incandescent tungsten filament suspended by support wires within a vacuum inside a glass bulb. As a result, they are highly susceptible to danage due to temperature variations and vibrations. The typical life of incandescent bulbs usually averages one or two thousand hours, so that they must be replaced several times a year.
LEDs, on the other hand, are more efficient than bulbs at converting electricity into light. LEDs are also durable and immune to filament breakage due to shock or vibration. Therefore, LEDs have a life span of approximately 50,000 hours versus one to two thousand hours for an incandescent bulb. This means that the bulbs do not have to be replaced nearly so often and do not require much maintenance. This is particularly important for marine lanterns that are difficult to access.
However, LEDs are not without their problems. Several of these problems are discussed in a paper entitled Design Considerations for Reliability and Optical Performance of LED Signal Lights given by Paul F. Mueller at the XVth IALA Conference, March 2002.
One problem is that typical low output 5 millimeter LEDs, generally used in lighting devices such as those used for marine and airport safety lights, only have a driving current ranging from about 50 to 70 milliwatts and put out insufficient lumens or candlepower to meet the 3-4 mile visibility requirement. Although it is possible to increase the optical output considerably by increasing the forward current above the nominal rated value, such an increase in forward current generally leads to premature failure due to overheating of the diode junction.
Alternatively, high-output LEDs, having a driving current of about 1-5 Watt with a high lumens output, can be used, but the heat generated by these high-output LEDs within the housing for the LEDs causes a precipitous reduction in service life for the LEDs.
Yet another approach to increasing the lumens produced by a light is to increase the efficiency of the light fixture. The lighting industry has used a parabolic reflector with fluorescent and other tubular lamps (such as those described in U.S. Pat. Nos. 4,992,695, 4,242,725, 4,388,675 and 3,829,677) to improve the efficiency of the light fixture. These patents describe lighting devices that reflect a portion of the light rays emitted from the tubular light source to form a beam of concentrated, parallel rays using a reflector having a parabolic or elliptic section.
The light sources of these devices, however, emit light rays in a full 360-degree format, as do the devices in U.S. Pat. Nos. 4,747,027, 6,053,624, 5,607,053, 4,034,217, 3,829,677, 6,585,397 B1. This 360-degree arrangement means that light rays from both the reflecting-emission side and the direct-emission side of the light source must be redirected to achieve the desired all-ray parallelism. Additional hardware (such as a diffuser or another reflector) is required to handle the light rays on the direct-emission side of these devices to achieve the all-ray parallelism. Some devices (such as U.S. Pat. Nos. 4,747,027, 6,053,624, 5,067,053, 4,388,675, 4,992,695, #4,242,725, 3,829,677, 6,585,397 B1) do not modify the paths of light rays emitted on the direct-emission side of the light source and, therefore, are not all-ray parallelism devices.
There is a need for a high-intensity lighting device with a single reflector assembly that redirects most of the light rays emitted from the light source into parallel rays towards a targeted illumination area.
There is also a need to provide a means of reducing the heat generated by a high-density lighting device.